Cancer is a chronic disease that impairs the quality of life. Therefore, in addition to cancer treatment, supportive treatment should be applied. It enables the control over the symptoms caused by cancer and suppresion of the side effects of various antitumor therapies. Cachexia reduces the functionality and quality of life of patients. Nutritional treatment is one form of supportive treatment aimed at preventing the development and reducing the progression of cachexia. In order to provide the best possible care, all oncology patients are screened for nutritional risk records and if the risk is significant an assessment of the patient's nutritional status is carried out. Various factors are included in the assessment: food intake, body mass index, assessment of body composition with various specific measurements, laboratory findings of CRP and albumin, physical examination focused on nutrition and functional status of the patient. The treatment itself begins with nutrition counseling and encouraging the patient to actively participate in the creation of a nutritional plan. Oral nutrition is the first choice and should be carried out as long as possible. If the nutritional status is still inadequate, oral nutritional supplements and artificial nutrition should be used. In addition to diet, treatment for cachexia includes strength, balance and endurance exercises that increase muscle mass, as well as medications that increase appetite and body weight and reduce inflammation.